TRW Microwave, Inc. (Building 825)

Bulletin Board

EPA is currently evaluating the potential for vapor intrusion in buildings overlying the shallow groundwater contamination area. On December 3, 2013 EPA sent a letter to the State of California's Regional Water Quality Control Board providing guidelines for vapor intrusion sampling and evaluation at this and 10 other South Bay State-lead sites.

Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 06/24/88

Final Date: 02/21/90

Deleted Date:

The former TRW Microwave Superfund Site (TRW Site), part of the “Triple Site” in Sunnyvale, California, is located at 825 Stewart Drive and neighbors multiple other sites, including: the Advanced Micro Devices (AMD) Buildings 901/902 Thompson Place Superfund Site (AMD 901/902 Site), the AMD 915 DeGuine Drive Superfund Site (AMD 915 Site), the Philips Semiconductors Site (Philips Site; formerly Signetics Inc.), which includes the properties at 811 Arques Avenue, 440 North Wolfe Road, and facilities along Stewart Drive, and the Mohawk Laboratories Site. A groundwater plume composed of volatile organic compounds (VOCs), including trichloroethene (TCE), extends from these sites more than a mile north in Sunnyvale to past Highway 101.

The TRW Site, together with three other operable units (OUs), was covered by a 1991 Record of Decision (ROD) for the Triple Site, all located in Sunnyvale. The four OUs for the Triple Site are as follows:

(1) The AMD 901/902 Site OU;
(2) The Philips Site OU;
(3) The TRW Microwave Site OU; and
(4) The Companies Offsite Operable Unit (OOU), a commingled plume of contaminants which originated from the other three operable units (and has contributions from other sites in the area).

At the time of adoption of the 1991 ROD, the OOU was defined as a 100-acre area, downgradient and north of the Triple Site in an area bounded by the Sunnyvale East Drainage Channel on the west and Santa Paula Avenue on the east, and as the area inside a 5 micrograms per liter (µg/L) isopleth for trichloroethene (TCE) in groundwater. Over 100 residences and at least 4 schools are present within the OOU.

The TRW Site was occupied by Aertech Industries from 1968 until it was sold to TRW, Inc (TRW). in 1984. In 1987, TRW sold the facility to FEI Microwave, Inc. In 1993 FEI Microwave stopped production and in 1995 the site was acquired by Stewart Associates and leased to research and development companies until 2001. The exterior of the building was remodeled between 2001 and 2003, including demolition of part of the existing structure and construction of a new two-story building. In December 2002, TRW merged with Northrop Grumman. In 2004, the property was purchased by Pacific Landmark, the current owner (as of 2013). During these changes in site ownership, TRW, and then Northrop Grumman retained responsibility for site cleanup.

The primary activity at the TRW Site was assembling and testing microwave components until semiconductor processing began in 1970. Primarily solvents and small quantities of acids were used in the assembly areas for semiconductors. Solvents, acids, and heavy metals were used in the fabrication areas and plating shop. The paint shop used paints and solvents.

Groundwater beneath the TRW Site is contaminated with volatile organic compounds (VOCs). Acid rinse water generated by the assembly processes was neutralized on-site and discharged to the City of Sunnyvale sewer system. An underground ammonia gas acid neutralization system was installed when the facility first opened. Floor drains and acid sinks in the plating shop were connected to buried plumbing that carried acid waste to the neutralization system. This system was closed in 1986, and the underground piping was sealed. The system was replaced with three aboveground tanks. Spent solvents were stored in one of four on-site underground tanks. After 1982, solvents were stored in drums and transported off-site. The closest residence is located approximately 1,200 feet north of the site. Municipal wells for the cities of Santa Clara and Mountain View tap a deep aquifer as a drinking water source that has not been affected by the contamination.

Contaminants and Risks

Contaminated Media

Groundwater

Soil and Sludges

VOC contamination was historically present in soil but has since been remediated to below regulatory criteria. Currently, groundwater contains various VOCs, however, institutional controls are in place to ensure that no one can ingests or come in direct contact with contaminated groundwater. Drinking water is not affected by the contamination. Drinking water in this area comes from the Hetch Hetchy Reservoir in the Sierra Nevada Mountains, and is regularly tested to ensure that it meets all applicable state and federal requirements.

A vapor intrusion investigation is currently ongoing at the one on-site building (which is currently unfinished and unoccupied), which indicates that vapor intrusion into the building is occurring (a process whereby vapors from the contaminated groundwater move upwards through the soil and enter the indoor air of nearby buildings). Additional investigation and mitigation work is underway to address the vapor intrusion risks, which will be completed prior to any tenants occupying the building.

Who is Involved

Investigation and Cleanup Activities

Initial Actions

Initial Actions: Four spent solvent underground tanks, along with some soil, were removed in 1973, 1976, 1980, and 1983. In 1984, 120 cubic yards of contaminated soils were excavated and transported to an EPA-approved hazardous waste facility. The site was backfilled to the surface with gravel and concrete was poured over the gravel to prevent rainwater from seeping into the pit. TRW installed and operated a soil vapor extraction (SVE) system in the vicinity of the former source area excavation from 1993 to 1998. Testing indicated that no further soil remediation was necessary and the SVE system was removed in 1998.

The water extraction pit created during the initial source area excavations was part of a groundwater extraction system operated by TRW between 1985 and 2001 to prevent VOCs from migrating off-site and to extract the groundwater for cleanup. On-site groundwater was treated by an air stripper and then discharged to Calabasas Creek. In 2000 and 2001, pumps in groundwater extraction wells were turned off to allow for site redevelopment activities and initiation of enhanced anaerobic bioremediation (EAB) in the former site source area. Based on groundwater testing that showed improved groundwater conditions, regulatory approval was received for continued shutdown of the groundwater extraction system.

Cleanup Ongoing

EAB was initially implemented in 2000 and has been ongoing in an effort to reduce contaminant concentrations at the TRW Site. Multiple injections of different EAB substrates have been performed since 2000 in and immediately downgradient of the former site source area, with the most recent injections performed in 2011.

In 1984, the State issued an order requiring AMD, Philips, and TRW to develop a joint plan to prevent further migration of contaminants. New orders in 1989 required TRW to submit an investigation and proposed cleanup plan with AMD and Philips. In 1991, the State and EPA issued a combined Record of Decision (ROD) for TRW and the surrounding AMD and Philips sites. The companies installed extraction wells to prevent migration of the VOC-impacted groundwater north of Highway 101. The extracted groundwater is treated at the Philips on-site treatment system.

Cleanup Results to Date

The removal of tanks and contaminated soil has reduced the potential for exposure to contaminated materials at the TRW Microwave (Building 825) site while groundwater continues to be treated. EAB activities have significantly reduced concentrations of VOCs detected in groundwater at the TRW site.

The third Five Year Review was completed in September 2009 and concluded that: the remedy at the TRW Site in Sunnyvale, California is currently protective of human health and the environment. EAB is ongoing at the site and continues to reduce contaminant concentrations. In the short-term, the institutional controls are preventing exposure to, and the ingestion of, contaminated groundwater.

A vapor intrusion investigation is currently ongoing at the one on-site building (which is currently unfinished and unoccupied), which indicates that vapor intrusion into the building is occurring (a process whereby vapors from the contaminated groundwater move upwards through the soil and enter the indoor air of nearby buildings). Additional investigation and mitigation work is underway to address the vapor intrusion risks, which will be completed prior to any tenants occupying the building.